Author
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Wesley, Ronald |
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Woods, Roger |
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Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/27/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Transmissible gastroenteritis (TGE) is economically an important disease of swine worldwide. It has been estimated to cost U.S. pig producers about 100 million dollars annually due to death and poor growth of infected pigs. To control this disease, maternal antibody from colostrum and post- colostral milk of immune sows is crucial in providing immediate protection for the suckling piglets. An understanding of the factors involved in the mechanisms of this protection in terms of the frequency of intake of antibody and the nature of the protective antibodies themselves would reduce economic losses due to the disease. We show that supplementing small quantities of pig antisera at least once a day is sufficient to protect piglets from dying from a TGEV infection although the infected piglets are still sick. This level of antisera supplementation is much less than the previously reported need to supplement every 4 hours for piglet survival. Moreover, we demonstrate that 2 unique monoclonal antibodies are involved in protective immunity. Ensuring that vaccinated sows response immunologically to these important antigenic sites will enhance or guarantee protection from possible TGE outbreaks. Technical Abstract: Passive protection experiments were conducted to determine the frequency and amounts of hyperimmune anti-serum needed to block a TGEV challenge infection and to identify monoclonal antibodies that are partially protective against TGEV. Hyperimmune anti-serum or monoclonal antibodies were supplemented in milk at each feeding or at selected feedings when the amount of antiserum was reduced. Three day old piglets were challenged with virulent virus that had been pre-incubated with antiserum or monoclonal antibodies. The results indicated that supplementing antiserum every other day was not efficacious for protection. Supplementing even small quantities of hyperimmune anti-serum (0.5 ml) at least once a day in most cases was sufficient for piglet survival but did not prevent morbidity. Increasing the amount (> 2 ml) and supplementing antiserum 3 times per day completely blocked the TGEV challenge infection. Two monoclonal antibodies were discovered that also provided passive protectio for baby pigs. One monoclonal antibody, 5G1, had a high neutralizing titer while the other, 6C4, was more effective in neutralizing and in binding to virulent TGEV than to attenuated TGEV. Both of these monoclonal antibodies were partially effective as supplements in milk for passive protection. Furthermore, these monoclonal antibodies were useful in boosting the efficacy of TGEV neutralizing colostrum which by itself was ineffective. These results show that other antigenic sites, different from the 4 well characterized epitopes on the S glycoprotein of TGEV, also are important for the passive protection. |
